The present invention relates to stethoscopes, and particularly stethoscopes having a plurality of input devices.
A stethoscope is a primary diagnostic tool utilized by physicians and is composed essentially of two ear pieces, an input unit, commonly known as a chest-piece, and two flexible hollow tubes which connect the chest-piece to the ear pieces. The tubes constitute, essentially, acoustic wave guides that confine acoustic pressure waves and transmit these waves from the chest-piece to the ear pieces.
The chest-piece of a stethoscope may be constituted by a single input device, or sound pickup, or by a plurality of such devices. When a plurality of devices are provided, the chest-piece will be composed of a coupler, or support, member connected to the flexible tubes and a turret which carries the sound pickups. The turret is rotatable to bring a selected pickup into a position for use, in which that pickup is in acoustic communication with the flexible tubes.
There are two basic types of pickup: those which are provided with a diaphragm; and those which are commonly referred to as bells. In the type provided with a diaphragm, the diaphragm is placed in contact with a region of the patient's body. Vibrations at the surface of the body are conveyed to the diaphragm and from there to an air space in communication with the diaphragm. The acoustic vibrations induced in the air space are then transmitted to the ear pieces via the hollow tubes. The pickups of the bell type have, as the name implies, a bell shape which is open at both ends. The larger diameter end of the bell is intended to be placed in contact with the patient's body, while the smaller diameter end is provided with an opening which communicates with the flexible tubes. Each type of pickup is suited to be used on certain parts of a patient's body to detect certain types of body sounds.
Known chest-pieces provided with a plurality of pickups include: chest-pieces provided with three pickups angularly offset from one another by 120.degree. about an axis of rotation of the turret on which the pickups are mounted, as shown, for example, in FIG. 4; chest-pieces having two pickups, one aligned with the longitudinal axis of the chest-piece and one oriented perpendicular to that longitudinal axis; and chest-pieces having two pickups spaced 180.degree. apart about the longitudinal axis of the turret, as shown, for example, in FIG. 5.
In the case of known chest-pieces of the first-mentioned type, one of the pickups is a bell having a relatively small maximum diameter and a relatively high ratio of depth to maximum diameter. This bell is well suited for monitoring heart sounds because it is able to fit completely between two adjacent ribs of an average patient and can thus be positioned so that the transmission of sounds to the bell is not obstructed by a rib. Known chest-pieces of the second- and third-mentioned types do not include the a bell having the form described above, but rather a comparatively larger diameter element which functions in the manner of a bell but which is too large to fit completely between the ribs of an average adult patient.
When a diaphragm type pickup is to be employed for listening to body sounds, sound detection can frequently be improved if the pickup is applied to a body surface with a firm, steady pressure. It is difficult for a user to apply such pressure with the known stethoscopes, either because there is no suitable pressure-applying surface located diametrically opposite the diaphragm, as in the prior art device shown in FIG. 4, or because the pickup located diametrically opposite the diaphragm has a shape which does not allow accurate and comfortable positioning of the user's finger to produce the requisite firm and steady pressure, as in the prior art device shown in FIG. 5.